Chambered doctor blade units, that is, doctor blade assemblies to strip ink off an anilox roller of a flexographic printing machine in which ink is supplied between two doctor blades to an ink chamber have been described in the literature reference "Technology of Flexography", Coating Verlag Thomas & Co., publishers. One form of such a chambered doctor blade is also shown in German Patent No. 37 04 433. These chambered doctor blade units are usually so constructed that an ink chamber or ink reservoir is at least partially bounded by two doctor blades, which each are secured to a carrier element forming the back-up or back structure for the doctor blades, see for example the referenced German Patent No. 37 04 443. Clamping strips attach the doctor blades to the holding structure. When the doctor blades are worn, it is possible to loosen the clamping connection by loosening screws, and replacing the doctor blade. Such chambered doctor blade units require substantial manufacturing effort since they are made of a plurality of parts which are releasably coupled together. Inserting a new doctor blade into an existing holding structure of the chambered unit requires care and skill to accurately align the front edge of the doctor blade parallel to the axis of the anilox roller which it is intended to strip.
U.S. Pat. No. 4,085,672, shows a structure which is closed all around, except for the opening to permit application of ink to an anilox roller and for an ink inlet opening. Ink is supplied to the chamber through a plurality of tubes or pipes. If it is necessary to replace the chambered doctor blade unit, a substantial number of couplings must be released. These couplings are formed as screw connections and also include a plurality of unions or pipe couplings for the respective ink supply tubes. Lateral distribution of the ink occurs, effectively, essentially only within the ink supply chamber.
When the chambered doctor blade unit is attached to a printing machine, a groove will match up with a marker on the machine to provide an indication for proper seating of the chambered unit, and to facilitate placing the chambered unit in appropriate position. The chambered doctor blade unit can be clamped and, although not shown, it is customary to clamp such units by screws or the like, since they are not further shown.
German Patent No. 37 04 433 also shows a chambered doctor blade unit in which a solid structural element is formed with an axially extending cross bore from which distribution bores extend directly into the chamber which then supplies ink to the anilox roller. The general idea is to distribute ink in the chamber before it actually reaches the chamber through the plurality of axially staggered exit openings or nozzles. The ink distribution duct, extending axially parallel to the anilox roller, thus is actually outside of the chamber structure of the chambered doctor blade unit.